Hrm...that could be interesting to play, actually. Every 100 coins you get a new "oLS, but then the 100 coins disappears. Unable to carry more than 99 coins at a time would eliminate protection...

Of course, for an evil twist: plumbers shouldn't be able to walk into monsters, but should be able to do combat solely through #jumping or spells (fireball being their favored spell, naturally)...hrm, what else?

Plumbers can normally jump one square away. After eating some types of fungus, this increases to two squares. Then, every time they encounter a fungus corpse of that type, it appears as a sunflower, and eating it provides a spell-like-ability along the lines of wand of fire with #monster. This fire beam bounces, and hits everything in the air in odd-numbered squares and everything on the floor in even-numbered squares.

Some new plumber-themed armor could be a cloak that allows a few turns of flight after a jump, a fuzzy suit that allows you to transform into a statue and back when #invoked (should this count as a possible cockatrice cure? hmmm...), and another full suit of armor that is described as a single shoe for some reason.